This invention relates to electromagnetically actuated electrical switch devices and more particularly to such devices generally characterized as crossbar switches presenting a coordinate array of electrical contacts.
Coordinate array electrical switches of the crossbar type in which electrical contacts are selectively operated by mechanical means responsive to electro-magnetic control have long constituted the basic switch unit of many telephone switching networks. Such switch units are widely used, for example, in the Bell System No. 5 switching system. Other coordinate switch arrangements providing metallic electrical contacts are also known. Miniature sealed reed switches as crosspoint elements, for example, are extensively employed in the more recent electronic telephone switching systems. Although considerable interest is presently being shown in the art in solid state coordinate switches, switches providing for the metallic contact control of circuit paths still offer a number of advantages in terms of transmission quality, reliability, and ease of maintenance, for example. The latter switches could be made even more attractive if their size and initial cost of fabrication were reduced and their construction simplified and efforts in the art to these ends also are known.
In the patent of S. L. Hjertstrand, U.S. Pat. No. 3,099,727, issued July 30, 1963, for example, is disclosed a coordinate switch arrangement in which a plurality of horizontal and vertical flexible, electrically conductive, magnetic strips intersect to define the coordinate array crosspoints and to constitute the controlled conducting paths. At a typical crosspoint a pair of magnetic contact plugs is affixed to one strip without making contact with the intersecting strip. A second plurality of horizontal and vertical conductive operating strips are mounted respectively on the magnetic strips to intersect between the contact plugs at each crosspoint. Briefly, when a selected pair of coordinate operating strips are energized by coincident currents, a resultant magnetic field closes through the intersecting magnetic strips and the crosspoint contact plugs to flex the magnetic strips toward each other at that point thereby bringing the plugs into electrical contact with the magnetic strip from which it is normally spaced apart. An electrical circuit is thus completed which remains closed as the result of the remanent character of the elements defining a crosspoint.
The foregoing prior art arrangement has been described in some detail for the purpose of providing a specific background and point of departure for the coordinate switch according to the present invention which is also directed to the problem of achieving a structurally simpler, more readily fabricated, and more economical crosspoint switch construction.
It is accordingly an object of this invention to simplify the construction of a coordinate switch beyond that hitherto possible and to achieve such a construction which more advantageously lends itself to automated fabrication techniques.
It is also an object of this invention to provide a new and novel coordinate switch construction which makes possible a significant increase in speed of operation compared to electromechanical crossbar switches and reduction in physical size compared to most coordinate switches.